Lubricating apparatuses are traditionally designed as pumping units which are mounted in close association with respective cylinders and which are connected with a feeding reservoir for lubricating oil and with lubricating points in the form of oil injection nozzles at different points on the cylinder wall. Each pump unit includes a plurality of reciprocating pumps that feed various lubricating points with oil and which are driven by a common rotating control shaft with cams provided thereon. By the rotation of the shaft, the cams with pressing heads act on respective axially displacing pistons which are spring biased in direction towards the control shaft, so that the pistons at the rotation of the shaft will perform reciprocating movements for activating the pistons of the reciprocating pumps.
It has also been proposed to adjust the pump stroke by means of a controllable motor, e.g. a step motor. This has been used for point lubrication, but it is difficult to establish in connection with conventional lubricating apparatuses. Such a system is e.g. disclosed in International patent application WO 02/35068 A1.
Furthermore, from DE 28 27 626 there is known a lubricating system based on lubricating oil supplied in measured quantities for predetermined time intervals through openings in the cylinder wall. Here, there is not indicated any possibility of a stepless controlling of the dosing to be performed at the individual lubricating points.
Furthermore, from GB 834533 A, DK 173512 B1 or CH 673506 A5 systems of the type mentioned in the introduction are known, where a hydraulic cylinder via a distributor plate or similar structure acts on a plurality of dosing pistons. In these designs, there will be one hydraulic cylinder for the activation. Here there is a need for separate adjusting means for quantity adjustment of the cylinder lubricating oil.
The present invention may be applied in connection with all kinds of lubricating apparatuses and methods based on hydraulic lubrication using hydraulic pistons and used for acting on injection units that include dosing pistons for the cylinder lubricating oil.